Terminal-cap and terminal connector construction for high voltage terminal bushings

ABSTRACT

An improved flexible diaphragm construction is provided for a high voltage terminal bushing in which the weld location between the inner periphery of the flexible diaphragm is at the upper outside extremity thereof, between the diaphragm and the thimble. In order to remove the diaphragm from the lead, an improved sealing gasket construction is provided, wherein a sealing gasket is placed in the thimble groove first, and at least one stop gasket is used to compress the sealing gasket. This also enables a separation between the thimble, when it is made of aluminum, from the copper terminal connector for electrolysis reasons. Additionally, the electrical transition joint between the aluminum and the copper, where these materials are used, is completely sealed from the atmosphere by such a gasketed construction.

United States Patent Inventor Charles W. Tragesser Murrysville, Pa.

Nov. 26, 1969 Aug. 3, 1971 Westinghouse Electric Corporation Pittsburgh, Pa.

Appl. No. Filed Patented Assignee TERMINAL-CAP AND TERMINAL CONNI'XITOR CONSTRUCTION FOR HIGH VOLTAGE TERMINAL IUSIIINGS 10 Claims, Drawingllgs.

U.S.Cl. 174/12 lll-l, 174/31 R Int. Cl. "11011: 17/26 FieldolSarclt 174/113. 12.3,14.3,l$.3,16.3,18, 31, 75, 75 D, 75 F, 152, 167

[56] References Cited UNITED STATES PATENTS 2,308,022 1/1943 Peterson et al. 174/31 X 3,204,022 8/1965 Soles et a1. 174/152 X Primary Examiner-Laramie E. Askin Attorneys-A. T. Stratton. C. L. Mellale and W. R. Crout ABSTRACT: An improved flexible diaphragm construction is provided for a high voltage terminal bushing in which the weld location between the inner periphery of the flexible diaphragm is at the upper outside extremity thereof, between the diaphragm and the thimble. In order to remove the diaphragm from the lead. an improved sealing gasket construction is provided, wherein a sealing gasket is placed in the thimble groove first, and at least one stop gasket is used to compress the sealing gasket. This also enables a separation between the thimble, when it is made of aluminum, front the copper terminal connector for electrolysis reasons. Additionally, the electrical transition joint between the aluminum and the copper, where these materials are used, is completely v sealedtrom the atmosphere by such a gasketed construction.

PATENTEU AUG 3 I971 SHEET 1 BF 2 COPPER FOR EXAMPLE ALUMINUM FOR EXAMPLE FIG. 3.

INVENTOR Charles W. Trogesser BY ATTORNEY PAIENIEIHUI; 3:911 ("3,597,521

sum 2 UF 2 EBIQLABI.

COPPER FOR EXAMPLE ALUMINUM FOR EXAMPLE SP6 GAS FOR EXAMPLE ALUMINUM FOR EXAMPLE ALUMINUM FOR EXAMPLE FIG 4.

CROSS-REFERENCE TO RELATED APPLICATIONS BACKGROUND OF THE INVENTION In the construction of terminal bushings, particularly of the high voltage type, it is customary to provide a bowl and an attaching flexible diaphragm to provide a hermetic seal, so that the oil-filled terminal bushing may be able to expand and contract with temperature changes during use of the terminal bushing. Additionally, since the rate of temperature expansion between the ceramic outer casings and the axially extending terminal lead may be different, there may occur longitudinal differential dimensional changes during ambient temperature variations, and the flexible diaphragm attempts to accommodate these changes. Note U.S. Pats. Nos. 2,292,031 Arnold and 2,285,594 Lingal in the connection.

It is, therefore, desirable to have a reliable flexible diaphragm, which will be able to flex the desired number of times, which constitutes the life of the terminal-bushing apparatus. US. Pat. No. 3,204,022, issued Aug. 31, I965, to otto H. Soles and Carl G. Lentjes, illustrates such a type of terminal bushing, which is under consideration. In the aforesaid Soles et a]. patent, a flexible diaphragm I8 is utilized to accommodate differential temperature expansions and constructions during the life of the equipment.

SUMMARY OF THE INVENTION According to a preferred embodiment of the present invention, a diaphragm is provided having flexibility throughout a long operational life, and the weld location is provided at a point, where there will be no stress concentrations imposed throughout the curvature of the diaphragm. Additionally, to provide a removable thimble-anddiaphragm construction from the lead of the terminal bushing, an improved sealing gasket and stop gasket construction is provided between the thimble and the terminal cap to thereby provide a removable construction, without resorting to welding.

It is, accordingly, a general object of the present invention to provide an improved welding construction for the flexible diaphragm ofa high voltage terminal bushing.

Another object of the present invention is to provide an improved sealing construction between the thimble ofa terminal bushing and the outer terminal cap, or terminal connector of the device, which enables an electrical isolation between the thimble and the terminal cap or connector.

Still a further object ofthe present invention is to provide an improved diaphragm attachment for a terminal bushing, in which the electrical transition joint between the aluminum and copper, where these materials are used, may be completely sealed from the surrounding atmosphere.

Further objects and advantages will readily become apparent upon reading the following specification, taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevational view of a high voltage terminal bushing embodying the present invention;

FIG. 2 illustrates, in an enlarged manner, a prior art welding construction and location, which was not satisfactory, and which led to undesirable stress concentrations imposed upon the flexible diaphragm leading to short life;

FIG. 3 illustrates the improved welding-and-sealing construction and location of the present invention, as applied particularly to an oil-filled high voltage terminal bushing; and,

FIG. 4 illustrates a modification of the present invention adaptable for a gas-filled type of high voltage terminal bushing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, and more particularly to FIG. 1 thereof, the reference numeral 1 generally designates a high voltage terminal bushing, which may be utilized in connection with a circuit breaker, as shown. It will be observed that the terminal bushing 1 includes an external weatherproof shell 2 of ceramic material, such as porcelain, a mounting flange assembly 3, a lower interiorly disposed porcelain shell 4, and a clamping flange ring 5. As shown, the'terminal bushing 1 is adaptable for mounting to a flange ring 7 associated with a fixed collar support 7 welded, as at 8, to the upper cover 9 of an enclosing structure, or tank 10 of the circuit breaker.

As well known by those skilled in the art, the enclosing tank structure I0 may be utilized for circuit breaker use. As illustrated in FIG. 1, the circuit breaker unit, or arc-extinguishing structure 11 is threadedly secured and clamped to the lower end 12 of the tubular terminal stud, or lead 13 extending axially through the terminal bushing 1.

For transformer use, a flexible lead from the transformer winding, not shown, may be threaded through the tubular terminal stud, or lead 13 an secured to an upper cap structure (not shown), associated with the upper external end of the terminal bushing 1.

FIG. 2 illustrates, to an enlarged scale, and in fragmentary manner, a prior art type of welding 15 of the diaphragm 16 to the upper sleevelike thimble 18 of the terminal bushing I of FIG. 1. A major design criteria for a diaphragm 16 is to be able to flex the desired number of times, which would constitute the life of the apparatus. A previous welding construction 15, at the location illustrated in FIG. 2, did not meet the test requirements of approximately 7,000 flexing cycles. The weld ing design 15 of attaching the diaphragm 16 to the thimble 18, as shown in FIG. 2, was the reason for not passing this test. The welding 15 located on the underside of the diaphragm I6 restricted the flexing action enough to cause stress concentration at the point designated by the reference letter A" in FIG. 2.

The changed construction, illustrated in FIG. 3 of the drawings, however, permits full flexing action to take place by not restricting the curvature of the diaphragm 16 from flexing. The weld location 20 is at the upper end of 16a of an axially extending surface portion 26 of the diaphragm element l6. The thimble 18 has an axially extending outer annular surface portion designated by the reference numeral 14. Tests on such a construction passed the rigid requirements. The diaphragm I6 of FIG. 3 did not break at 12,000 cycles. Additionally, this has enabled the substitution of aluminum for copper in the flexible diaphragm element 16.

A metallic bowl 21, previously formed of copper, but more economically made of aluminum, under the new construction, is welded, as at 19, to the outer side of the diaphragm 16, as shown. A confinement ring 17, for the brazing material is affixed to the inner wall of the bowl 21.

Another important feature of the present invention is the method of sealing around the stud, or lead 13. Because it is desirable to be able to remove the diaphragm 16 from the stud or lead 113, welding at the point B" cannot be done, particularly when construction is desired for an oil-filled type of terminal bushing. The arrangement of the present invention incorporates a neoprene rubber gasket 22 and two hard gaskets 24, 25 of asbestos neoprene, for reliability, The sealing gasket 22 is placed in the thimble groove 18a first. When compressed, it will manufactured fill the threads 13a of the lead 13. The small stop gasket 24 is used to compress the sealing gasket 22 below the thimble 18, before it fills in the threads 13a. This insures that the sealing gasket 22 is completely captivated, and-will not extrude out of the groove 18a in the thimble 118. The large stop gasket 25 is then used to compress the sealing gasket 22, and also to separate the aluminum thimble 18 from the copper terminal 27 for electrolysis reasons. The design has been experimentally tried in a temperature cycle of 40 C to 105 C. with 20 p.s.i.g. air in the bowl 21. A total of 70 cycles were performed on four bowls 21 without any gasket leaks.

Another important feature of the present invention is to have the electrical transition joint between the aluminum and copper elements 18,27 completely sealed from the surrounding atmosphere A neoprene disc gasket 31 is used at the extreme upper end of the lead 13 in the base 27a of the cupshaped terminal connector 27. it will be noted that the joint is sealed at the top and bottom of the joint with the neoprene gasket 22, 31. For additional reliability, it is also preferable to use an electrical joint compound such as Alcoa 2" manufactured by Aluminum Company ofAmerica, to insure reliability. This is designated by the reference numeral 40 in FIG. 3. The foregoing construction describes an application of the present invention to an oil-filled terminal bushing of the type set forth in U.S. Pat. Nos. 2, 853,538-Frakes, and 3,101,386-Cronin et al. For use in a gas-filled terminal bushing, such as one utilizing sulfur-hexaflouride (SF gas, for example, such as illustrated in U.S. Pats. Nos. 3,33l,9l8--Sonnenberg et al. 3,178,504-Frakes et al. 3,173,988Martahus et al. 3,160,70l-King et al. and 3,059,044Friedrich et al. a slightly different construction may be utilized, such as set forth in FIG. 4 of the drawings.

With reference to FIG. 4, it will be observed that the weld location 20 is the same as in FIG. 3', however, it will be observed that in this instance the thimble 18A is solid and continuous at its upper end, and is provided with threaded recess 188 to thereby threadedly accommodate the axially extending stud or lead 13A.

The terminal or connector 27A, preferably of copper, has a flange portion 278, which is bolted, as by bolts 33, to a coplanar portion 18C of the thimble 18A. Preferably, the thimble 18A is of aluminum. A gasket 35 provides a seal to the atmosphere of the electrical joint 36 between the thimble 18A of aluminum and the terminal connector 27A of copper.

Although there has been illustrated and described specific structures, it is to be clearly understood that the same were merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art, without departing from the spirit and scope of the invention.

I claim:

1. A terminal bushing having an axially extending conducting lead for carrying current through the terminal bushing, a metallic thimble surrounding the lead and secured thereto at the upper external end of the terminal bushing, said thimble having an axially extending outer annular surface portion, a relatively thin flexible diaphragm for accommodating differential temperatures expansions of the terminal bushing and provided with a central opening therethrough and an inner axially extending portion, said thimble protruding through said opening in the diaphragm, and the diaphragm being welded to the thimble at said axially extending portion and at the upper open extremity ofthe axially extending portion.

2. The combination of claim 1, wherein the diaphragm is made ofaluminum.

3. The combination of claim 2, wherein the thimble is also made of aluminum.

4. The combination of claim 1, wherein the metallic thimble is threadedly secured to the axially extending lead.

5. The combination of claim 1, wherein an aluminum bowl is secured to the outer periphery of the flexible diaphragm.

6. A terminal bushing having an axially extending conducting lead for carrying current through the terminal bushing, a metallic thimble surrounding the lead and secured thereto at the upper external end of the terminal bushing, a relatively thin flexible diaphragm for accommodating differential temperature expansions of the terminal bushing and provided with a central opening therethrough, said thimble protruding through said opening in the diaphragm, the diaphragm being welded to the thimble at the upper extremity of the opening, the metallic thimble being threadedly secured to the axially extending lead, the thimble having a groove formed therein, an elastomeric sealing gasket being disposed within the thimble groove, and a cup-shaped terminal connector being threaded over the upper extremity of the lead to compress the sealing gasket.

7. The combination according to claim 6, wherein at least one stop gasket is interposed between the cup-shaped terminal connector and the elastomeric sealing gasket.

8. A terminal bushing having an axially extending conducting lead for carrying current though the terminal bushing, a metallic closure cap thimble surrounding the lead and secured thereto at the upper external end of the terminal bushing, said closure cap thimble having an upper planar portion, a relatively thin flexible diaphragm for accommodating differential temperature expansions of the terminal bushing and provided with a central opening therethrough, said closure cap thimble protruding through said opening in the diaphragm, the diaphragm being welded to the thimble at the upper extremity of the opening, and a terminal connector having a lower planar portion abutting the upper planar portion of the closure cap thimble.

9. The combination of claim 8, wherein ring-shaped gasket means is interposed between confronting faces of the terminal and the closure cap thimble.

10. The combination according to claim 9, wherein the terminal connector is of copper and the closure cap thimble is of aluminum. 

1. A terminal bushing having an axially extending conducting lead for carrying current through the terminal bushing, a metallic thimble surrounDing the lead and secured thereto at the upper external end of the terminal bushing, said thimble having an axially extending outer annular surface portion, a relatively thin flexible diaphragm for accommodating differential temperatures expansions of the terminal bushing and provided with a central opening therethrough and an inner axially extending portion, said thimble protruding through said opening in the diaphragm, and the diaphragm being welded to the thimble at said axially extending portion and at the upper open extremity of the axially extending portion.
 2. The combination of claim 1, wherein the diaphragm is made of aluminum.
 3. The combination of claim 2, wherein the thimble is also made of aluminum.
 4. The combination of claim 1, wherein the metallic thimble is threadedly secured to the axially extending lead.
 5. The combination of claim 1, wherein an aluminum bowl is secured to the outer periphery of the flexible diaphragm.
 6. A terminal bushing having an axially extending conducting lead for carrying current through the terminal bushing, a metallic thimble surrounding the lead and secured thereto at the upper external end of the terminal bushing, a relatively thin flexible diaphragm for accommodating differential temperature expansions of the terminal bushing and provided with a central opening therethrough, said thimble protruding through said opening in the diaphragm, the diaphragm being welded to the thimble at the upper extremity of the opening, the metallic thimble being threadedly secured to the axially extending lead, the thimble having a groove formed therein, an elastomeric sealing gasket being disposed within the thimble groove, and a cup-shaped terminal connector being threaded over the upper extremity of the lead to compress the sealing gasket.
 7. The combination according to claim 6, wherein at least one stop gasket is interposed between the cup-shaped terminal connector and the elastomeric sealing gasket.
 8. A terminal bushing having an axially extending conducting lead for carrying current though the terminal bushing, a metallic closure cap thimble surrounding the lead and secured thereto at the upper external end of the terminal bushing, said closure cap thimble having an upper planar portion, a relatively thin flexible diaphragm for accommodating differential temperature expansions of the terminal bushing and provided with a central opening therethrough, said closure cap thimble protruding through said opening in the diaphragm, the diaphragm being welded to the thimble at the upper extremity of the opening, and a terminal connector having a lower planar portion abutting the upper planar portion of the closure cap thimble.
 9. The combination of claim 8, wherein ring-shaped gasket means is interposed between confronting faces of the terminal and the closure cap thimble.
 10. The combination according to claim 9, wherein the terminal connector is of copper and the closure cap thimble is of aluminum. 